Shear-induced anisotropic microstructure in phase-separated biopolymer mixtures

• Published in: Food hydrocolloids 2000-05, Vol.14 (3), p.217-225
• Main Authors: Wolf, B., Scirocco, R., Frith, W.J., Norton, I.T.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biopolymer mixtures; Disperse state. Micelles; Food additives; Food industries; Fundamental and applied biological sciences. Psychology; Gelatin–guar; Gellan–sodium alginate; Gellan–κ-carrageenan; General aspects; Interfacial tension; Microstructure; Molecular biophysics; Phase-separation; Physico-chemical properties of biomolecules; Rheology
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/S0268-005X(99)00062-4

This work is concerned with the formation, under flow, of regular, anisotropic particle shapes in phase separated liquid–liquid biopolymer mixtures (water-in-water emulsions) and the fixing of such structures through gelation of one or both phases. Hypothesising that, for the purpose of flow processing, such water-in-water emulsions can be treated in the same manner as conventional emulsions, a shear flow process was chosen. Microstructures produced by this route show a wide spectrum of shape, from spherical particles, developed at the lower end of the shear stress range, to long extended particles, as well as irregularly shaped particles, formed at higher shear stresses. These different microstructures developed are discussed in the context of viscosity and shear rate data recorded during the structuring process. For one of the mixtures, the viscosity ratio and interfacial tension between the two phases were quantified. It was found that the observed particle deformations in this mixture coincided with predictions from droplet deformation theories.